Suppose I have a function like this.
-(NSData *)getData {
NSData *myData = [[NSData alloc]init];
return myData;
}
-(void)displayData {
NSData *data = [self getData];
//convert data to string
data = [self getData];
//Convert data to string
data = [self getData];
//convert data to string
[data release];
}
Here I call get data three times and assign to same object but releasing only once. So does this steps leak memory ?
It must be a non-arc project since [self release] is compiling. If that's the case, then yes, the code you posted leaks two empty NSData instances each time displayData is called.
In an arc project, the static analysis will insert releases before each assignment avoiding the leaks.
you have to write getData() as below , you need to specify autorelease in getdate() , otherwise memory leak will occur
-(NSData *)getData {
NSData *myData = [[[NSData alloc]init] autorelease];
return myData;
}
-(void)displayData
{
NSData *data = [[self getData] retain]; // since getdata giving you an autoreleased object
//before assigning new value , you have to take care of old value .
[data release];
data = nil;
//convert data to string
data = [[self getData] retain];
[data release];
data = nil;
//Convert data to string
data = [[self getData] retain];
[data release];
data = nil;
}
Related
I am developing application which required image caching. For doing this, I am using JMImageCache library. It is work fine for caching. But It can not release memory occupied by
following line.
[NSData dataWithContentsOfFile]
Here, is function which content code for cache image from disk.
- (UIImage *) imageFromDiskForURL:(NSString *)url {
NSData *data = [NSData dataWithContentsOfFile:cachePathForURL(url) options:0 error:NULL];
UIImage *i = [[[UIImage alloc] initWithData:data] autorelease];
data = nil;
[data release];
return i;
}
I have check it with instruments and it alloc 2.34 MB each time.
data = nil;
[data release];
Why do you expect this at all to work? Why should this release the original data? You're sending the release message to nil, which is a no-op.
Furthermore, if you don't create the object using alloc or copy, then it's autoreleased. That means if you release it once more, it will be overreleased and most likely your app is going to crash. What you need is:
One. Wrap the method call in an explicit autorelease pool:
- (UIImage *)imageFromDiskForURL:(NSString *)url
{
UIImage *i;
#autoreleasepool {
NSData *data = [NSData dataWithContentsOfFile:cachePathForURL(url) options:0 error:NULL];
i = [[UIImage alloc] initWithData:data];
}
return [i autorelease];
}
Two, alloc-init or manually release the data object:
- (UIImage *)imageFromDiskForURL:(NSString *)url
{
NSData *data = [[NSData alloc] initWithContentsOfFile:cachePathForURL(url) options:0 error:NULL];
UIImage *i = [[[UIImage alloc] initWithData:data] autorelease];
[data release];
return i;
}
alter the sequence nil and release
[data release];
data = nil;
and for clearing the cache use following delegate methods
[[JMImageCache sharedCache] removeAllObjects];
[[JMImageCache sharedCache] removeImageForURL:#"http://dundermifflin.com/i/MichaelScott.png"];
read the read me file of library
https://github.com/jakemarsh/JMImageCache/blob/master/README.markdown
What you are trying to do cannot work due to the way how UIImage uses a data you pass it. The data object is retained by the image, or more precisely by a CGImageSource that the UIImage has internally. From this data it is able to decompress and create the image any time. There is an option on CGImageSource to also keep around the decompressed data, but UIImage does not use that because it optimized for small UI graphics.
One thing that you can do to alleviate memory pressure is to not load the entire NSData into memory, but to memory-map it instead. This makes creation or recreation of the image a tad slower, but the created NSData object is very small in comparison.
I am trying to downloading more then 600 images in loop with a progress meter on the top of the screen to the user. I blocked my screen with a fade layer for showing activity and progress.
I am getting the memory warning message in between and app getting crashes.
My steps to reach the loop are :
On app delegate, I check first core data table for all rows which is having "0" value in isImageAvailable bool field.
If shows me some count (say 600), and I show and alert with YES and NO option.
On YES : [self performSelector:#selector(myDownload:) withObject:nil afterDelay:0.2];
in myDownload
NSOperationQueue *queue = [NSOperationQueue new];
// Create our NSInvocationOperation to call loadDataWithOperation, passing in nil
NSInvocationOperation *operation = [[NSInvocationOperation alloc] initWithTarget:self
selector:#selector(startUpdatingRecords:) object:nil];
// Add the operation to the queue
[queue addOperation:operation];
[operation release];
[queue release];
in startUpdatingRecords :
-(void)startUpdatingRecords:(id)sender
{
[self performSelectorInBackground:#selector(updateProgressMeter:) withObject: [NSString stringWithFormat:#"%d",self.loopStartIndex]];
// Variable declarations
CGSize newSizeLarge ;
NSPredicate *predicate;
NSMutableArray *MatchingID;
Image_DB *data;
// Cache Directory path
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);
NSData *responseData; // = [[NSData alloc]init] ;
NSURL *url = [[[NSURL alloc]init] autorelease];
NSMutableURLRequest *request = [[[NSMutableURLRequest alloc]init] autorelease];
UIImage *imgSelected_Large = [[[UIImage alloc]init] autorelease];
// Loop through all IDs
for (int i = 0; i < [self.arrayOfID count]; i++) //for (int i = loopStart; i < loopEnd; i++)
{
if (self.abortDownload)
{
break;
}
NSString *documentsDirectory = [[[NSString alloc] initWithFormat:#"%#",[paths objectAtIndex:0]] autorelease];
documentsDirectory = [paths objectAtIndex:0];
documentsDirectory = [documentsDirectory stringByAppendingFormat:#"/ImageFolder"]; // Image folder path
myClass *classObj = [self.arrayOfID objectAtIndex:i];
NSString *strURl = [[[NSString alloc] initWithFormat:#"%#%#", self.MyURL,recipeObj.recipeImageStr] autorelease];
//NSLog(#"URL = %#",strURl);
url = [NSURL URLWithString:strURl];
request = [NSMutableURLRequest requestWithURL:url];
responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:NULL error:NULL]; // Get Image Data into NSData
//imgSelected_Large = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:strURl]]];
NSLog(#"Download Count = %d",i+1);
if (responseData != nil)
{
imgSelected_Large = [UIImage imageWithData:responseData];
// Resizining image
newSizeLarge.width = 320;
newSizeLarge.height = 180;
imgSelected_Large = [self imageWithImage:imgSelected_Large scaledToSize:newSizeLarge]; // New sized image
NSData *dataPhoto; // no need to release it because UIImageJPEGRepresentation gives autoreleased NSData obj.
dataPhoto = UIImageJPEGRepresentation(imgSelected_Large, 0.6); // Set new image representation and its Compression Quality
documentsDirectory = [documentsDirectory stringByAppendingPathComponent:[NSString stringWithFormat:#"Image_%d", classObj.nodeID]];
[dataPhoto writeToFile:documentsDirectory atomically:YES]; //Write file to local folder at default path
predicate = [NSPredicate predicateWithFormat: #"(image_ID = %d )",recipeObj.nodeID];
MatchingID = [CoreDataAPIMethods searchObjectsInContext:#"Image_DB" :predicate :#"image_ID" :YES :self.managedObjectContext];
// Setting flag variable for available image
for (int j = 0; j< [MatchingID count]; j++)
{
//Assign the Authors Records in Class Object and save to Database
data = (Image_DB*) [MatchingID objectAtIndex:j];
// data.image_large = dataPhoto; // Code for storing BLOB object to DB
data.extra_1 = #"1";
//NSLog(#"Flag updated");
}
}
// Exit out code
if ( i == [self.arrayOfID count] - 1 || i == [self.arrayOfID count]) // Its the last record to be stored
{
NSError *error;
if (![self.managedObjectContext save:&error])
{
// Handle the error...
NSLog(#"Error in updating %#",error);
}
self.isUpdateImageCalled = NO;
[self performSelectorOnMainThread:#selector(removeProgressMeter) withObject:nil waitUntilDone:NO];
}
// Update UI screen while in downloading process
[self performSelectorInBackground:#selector(updateProgressMeter:) withObject:[NSString stringWithFormat:#"%d",self.loopStartIndex+i+1]];
}
}
If I didn't release responseData then my app shows me memory warning and got crashed. If I released then, [NSConcreteMutableData release]: message sent to deallocated instance 0x1e931de0 error occures.
How to refine my code. Can any one suggest me on my code and rework and make a refined code.
Please please help me out.
Your responseData returned by sendSynchronousRequest is autoreleased thus you shouldn't release it yourself. For the first sight I don't see a memory leak in your code. It is possible that your application actually uses too much memory, without leaking it. Try to place an autorelease pool inside your for cycle:
for (...) {
NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
// your original code with a lot of autoreleased objects
[pool release];
}
If you wrap your code within an autorelease pool, all objects that are sent the autorelease message inside the wrap will be actually released when the pool itself is released: this way you purge the memory in every for cycle.
See also Using Autorelease Pools in the doc, it specifically mentions that you should use them in the case "if you write a loop that creates many temporary objects".
Should I check if a file exists at a given path when trying to read the data into an NSData object? Right now I'm not doing at the moment but my code works since my array that is supposed to get populated with data from the file will be set to nil and I can later in my application check if that array is nil. But I'm thinking that the code is perhaps "ugly" and would work better if i did a check (like the one in the commented code).
NSData *codedData = [[NSData alloc] initWithContentsOfFile:[CareersParser dataFilePath]];
/*
if (codedData != nil) {
//do the below (not commented out code)
} else {
//file doesn't exist at the given path
[codedData release];
return nil;
}
*/
NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:codedData];
NSArray *careers = [unarchiver decodeObjectForKey:kDataKey];
[unarchiver finishDecoding];
NSMutableArray *ids = [[NSMutableArray alloc] init];
for (Career *career in careers) {
[ids addObject:[career id]];
}
// Sort the array in an orderly fashion
NSArray *sortedIds = [ids sortedArrayUsingSelector:#selector(caseInsensitiveCompare:)];
// Release allocated memory
[ids release];
[unarchiver release];
[codedData release];
return sortedIds;
That seems sensible to me I would reverse the if statement to do away with the else clause.
if (nil == codedDate) {
[codedData release];
return nil;
}
... Do the rest of your code
Apple suggests here that you should attempt to perform an operation such as loading data like you have suggested. As long as you don't try to do [[NSManager defaultManager] fileExistsAtPath:path] you won't be introducing race conditions.
You don't, and this could introduce a race, so it will be more "ugly". Just check if codedData if nil in case of reading failure.
I have a function which use for read one single line from a csv file.
But I got a release of previously deallocated object error, or sometimes the it is "double free" error.
I try to track down which object causes this error base on the error memory address, but I failed to do this.
Here's the code:
#interface CSVParser : NSObject {
NSString *fileName;
NSString *filePath;
NSString *tempFileName;
NSString *tempFilePath;
//ReadLine control
BOOL isFirstTimeLoadFile;
NSString *remainContent;
}
#property(nonatomic,retain) NSString *fileName;
#property(nonatomic,retain) NSString *filePath;
#property(nonatomic,retain) NSString *tempFileName;
#property(nonatomic,retain) NSString *tempFilePath;
#property(nonatomic,retain) NSString *remainContent;
-(id)initWithFileName:(NSString*)filename;
-(BOOL)checkAndCopyFile:(NSString *)filename;
-(BOOL)checkAndDeleteTempFile;
-(NSString*)readLine;
-(NSArray*)breakLine:(NSString*)line;
#end
#implementation CSVParser
#synthesize fileName;
#synthesize filePath;
#synthesize tempFileName;
#synthesize tempFilePath;
#synthesize remainContent;
-(id)initWithFileName:(NSString *)filename{
//ReadLine control
isFirstTimeLoadFile = TRUE;
self.fileName = filename;
self.tempFileName = [[NSString alloc] initWithFormat:#"temp_%#",fileName];
NSArray *documentPaths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentDir = [documentPaths objectAtIndex:0];
self.filePath = [documentDir stringByAppendingPathComponent:fileName];
self.tempFilePath = [documentDir stringByAppendingPathComponent:tempFileName];
if ([self checkAndCopyFile:fileName]) {
return self;
}else {
return #"Init Failure";
}
}
-(BOOL)checkAndCopyFile:(NSString *)filename{
BOOL isFileExist;
NSError *error = nil;
NSFileManager *fileManger = [NSFileManager defaultManager];
isFileExist = [fileManger fileExistsAtPath:filePath];
if (isFileExist) {
//Create a temp file for reading the line.
[fileManger copyItemAtPath:filePath toPath:tempFilePath error:&error];
return TRUE;
}else {
return FALSE;
}
}
-(NSString*)readLine{
NSError *error = nil;
//Read the csv file and save it as a string
NSString *tempFirstLine = [[[NSString alloc] init] autorelease];
NSString *stringFromFileAtPath = [[NSString alloc] init];
if (isFirstTimeLoadFile) {
NSLog(#"Into First Time");
stringFromFileAtPath = [NSString stringWithContentsOfFile:tempFilePath
encoding:NSUTF8StringEncoding
error:&error];
isFirstTimeLoadFile = FALSE;
}else {
NSLog(#"Not First Time");
NSLog(#"Not First Time count:%d",[remainContent retainCount]);
stringFromFileAtPath = remainContent;
remainContent = nil;
}
if ([stringFromFileAtPath isEqualToString:#""]) {
[stringFromFileAtPath release];
return #"EOF";
}
//Get the first line's range
NSRange firstLineRange = [stringFromFileAtPath rangeOfString:#"\n"];
//Create a new range for deletion. This range's lenght is bigger than the first line by 1.(Including the \n)
NSRange firstLineChangeLineIncludedRange;
if (stringFromFileAtPath.length > 0 && firstLineRange.length == 0) {
//This is the final line.
firstLineRange.length = stringFromFileAtPath.length;
firstLineRange.location = 0;
firstLineChangeLineIncludedRange = firstLineRange;
}else {
firstLineRange.length = firstLineRange.location;
firstLineRange.location = 0;
firstLineChangeLineIncludedRange.location = firstLineRange.location;
firstLineChangeLineIncludedRange.length = firstLineRange.length + 1;
}
//Get the first line's content
tempFirstLine = [stringFromFileAtPath substringWithRange:firstLineRange];
remainContent = [stringFromFileAtPath stringByReplacingCharactersInRange:firstLineChangeLineIncludedRange withString:#""];
[stringFromFileAtPath release];
error = nil;
return tempFirstLine;
}
And the following code shows how I use the class above:
CSVParser *csvParser = [[CSVParser alloc] initWithFileName:#"test.csv"];
BOOL isFinalLine = FALSE;
while (!isFinalLine) {
NSString *line = [[NSString alloc] init];
line = [csvParser readLine];
if ([line isEqualToString:#"EOF"]) {
isFinalLine = TRUE;
}
NSLog(#"%#",line);
[line release];
}
[csvParser release];
If I run the code, and finish the csv parsing, the App's main function will give me the double free error when it try to free the autorelease pool."* __NSAutoreleaseFreedObject(): release of previously deallocated object (0x6a26050) ignored"
NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
int retVal = UIApplicationMain(argc, argv, nil, nil);
Could someone help me solve this issue?
Thank you!
[pool release];
Do not use -retainCount.
The absolute retain count of an object is meaningless.
You should call release exactly same number of times that you caused the object to be retained. No less (unless you like leaks) and, certainly, no more (unless you like crashes).
See the Memory Management Guidelines for full details.
There are a few problems in your code:
you aren't following the correct init pattern. You should have a self = [super init...]; if (self) {...} in there somewhere.
tempFileName is a retain property and you assign it the result of alloc/init. It will be leaked.
An immutable empty string ([[NSString alloc] init]) is pretty much never useful. And, in fact, stringFromFileAtPath is being leaked (technically -- implementation detail wise there is an empty immutable singleton string and thus, no real leak, but.... still...)
Finally, the crash: your readLine method correctly returns an autoreleased object. Yet, your while() loop consuming the return value of readLine is also releaseing that return value, leading to a double-release and an attempt to free that which was already freed.
You should "build and analyze" your code. I bet the llvm static analyzer would identify most, if not all, of the problems I mentioned above (and probably some more I missed).
When building with the analyzer, do you have either "all messages" or "analyzer issues only" selected in the Build window? Because, looking at the code, I'm surprised the analyzer didn't catch the obvious problem with stringFromFileAtPath.
Excerpting the code, you have the following lines that manipulate stringFromFileAtPath:
NSString *stringFromFileAtPath = [[NSString alloc] init];
....
stringFromFileAtPath = [NSString stringWithContentsOfFile:tempFilePath
encoding:NSUTF8StringEncoding
error:&error];
....
stringFromFileAtPath = remainContent;
....
[stringFromFileAtPath release];
And remainContent is set by:
remainContent = [stringFromFileAtPath stringByReplacingCharactersInRange:firstLineChangeLineIncludedRange
withString:#""];
You are releasing an autoreleased object. By memory keeps going up, how are you measuring it? Don't use Activity Monitor as it is nearly as useless to developers as retainCount is misleading. Use Instruments.
Your tempFirstLine NSString object is declared with autorelease, and is returned as your NSString line, which is then released.
Try using this:
while (!isFinalLine) {
NSString *line = [csvParser readLine];
if ([line isEqualToString:#"EOF"]) {
isFinalLine = TRUE;
}
NSLog(#"%#",line);
}
Replac this:
NSString *stringFromFileAtPath = [[NSString alloc] init];
with this:
NSString *stringFromFileAtPath = nil;
and get rid of the [stringFromFileAtPath release] statements.
The first line creates a pointer to a new string object that you never use, because you immediately overwrite the pointer with a pointer to string objects from elsewhere, which you don't need to release because you don't own them/didn't create them. Since you are releasing them, you're getting a crash.
You make the same mistake with tempFirstLine.
I am new to ObC and have a problem that i just cant fix. There may be other issues as well but the main issue is this:
Starting the app
Press button = load new view
In the new viewDidLoad i call another object/function and send a NSMutableArray
Process data and send back a NSMutableArray
App crash, see comment where. Most often when i go back and back again but sometimes the first time
As i am new to this i guess i do a lot of this wrong but could someone nice take a look at the code and give me some advice. I would assume i have problem with releasing something.
- (void)viewDidLoad {
[super viewDidLoad];
NSLog(#" ");
NSLog(#"viewDidLoad ");
NSLog(#" ");
NSLog(#">>Processing prepareGame<<");
NSMutableArray *propArray1 = [[NSMutableArray alloc] initWithObjects:#"9999", nil]; //Init with dummy numbers
AccessPropertiesFile *readMyProperties = [AccessPropertiesFile new]; //Init function call to read file
NSLog(#"Prepare to call readProperties");
propArray1 = [readMyProperties readPropertiesFile:propArray1];
NSLog(#"Back from readProperties:error after this");
/*
for (NSString *element in propArray1) {
NSLog(#"Elements in prop2Array; %#", element);
}
*/
[readMyProperties release];
[propArray1 release];
}
-(NSMutableArray *)readPropertiesFile:(NSMutableArray *)readDataArray {
NSLog(#"Processing readProperties");
// For error information
NSError *error;
//Prepare File Manager
NSString *filePath = [self dataFilePath];
NSFileManager *fileMgr;
fileMgr = [NSFileManager defaultManager];
NSArray *propertiesArray = [NSArray alloc]; //Alloc array
//Check from what module the call is coming from to ecide what to do
if ([fileMgr fileExistsAtPath: filePath] == NO) {
NSLog (#"File not found");
//File does not exists, this is the first time the game starts
//Set up default parameters
NSString *fileString =#"0\n30\n30\n10\n1\n1\n1\n2\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n1\n";
// Write default parameters to file
[fileString writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:&error];
propertiesArray = [fileString componentsSeparatedByString:#"\n"]; // each line, adjust character for line endings
}
else { //File exists
NSLog (#"File exists");
NSString *fileString = [NSString stringWithContentsOfFile:filePath
encoding:NSUTF8StringEncoding error:nil]; // reads file into memory as an NSString
propertiesArray = [fileString componentsSeparatedByString:#"\n"]; // each line, adjust character for line endings
}
//Clean readDataArray
[readDataArray removeAllObjects];
//Populate return array
for (NSString *element in propertiesArray) {
//NSLog(#"Elements in propertiesArray; %#", element);
[readDataArray addObject:element];
}
NSLog(#"readDataArray: %#", readDataArray);
[propertiesArray release];
[readDataArray autorelease];
NSLog(#"returning from readProperties");
return readDataArray;
}
#end
You are over-releasing readDataArray (known as propArray1 in the method that didn't create it). You create it and autorelease it in your second method, then you release it again at the end of your first method (where it wasn't created).
I suggest you use Analyze feature that comes with latest XCode. It is a good feature that I always use to track if I forget to release or release too much.
I also spotted that you also over-release the propertiesArray because it contains the result from [fileString componentsSeparatedByString:], which will be autorelease according to Cocoa convention.